6 Weeks...or 5 Months?

What creature has a very short life span in the warm months yet can live several times longer in the challenging cold of winter? That is precisely the reality for the worker bee.

The survival of bees during the winter is a story of epic preparation and a huge collaborative effort within the hive, from late fall to the onset of winter.

Worker bees that live in the warmer months have a hard and disciplined life ahead of them. From the moment they extract themselves from the cell to the last flap of their wings, they are aptly named workaholics. Their industry puts great stress on their tiny bodies and they use a huge amount energy in working so diligently.

The end result is a lifespan of around 6 weeks.

By comparison, the worker bee that lives through the winter months has a much more focused, singular role. Her sole objective is to see the queen through to the spring, at which time the queen can start laying eggs.

The winter worker bee is a bridge from one generation of the queen's offspring to another. Her reward for seeing the queen through this challenging period is the potential to live from early winter to spring.

Months, not weeks....

Stores for the Winter

We are used to seeing our bees venture away from the hive during the warmer months, but that is not an option during the winter. The temperatures are too low and other risks such as bad weather and starving pests simply make this impossible.

And so, bees prepare at great length for the oncoming winter by building stores of honey within the hive. This store represents their lifeline for reaching the spring and they are entirely dependent on having enough honey to see them through that period.

Beekeeper caution

A beekeeper is advised not to take honey from a first-year beehive, giving the bees the best chance of surviving winter.

The amount of honey required to survive the winter depends on the depth and duration of the winter. In warmer climates, 30 lbs. or so may be adequate but the harsh, colder winters in the north may require as much as 100 lbs. That's a very considerable burden on the first-year colony.

Out With The Drones

There are a number of ways in which bees prepare for the winter. Their store of honey is a heavily protected resource and anything that limits how long it will last is considered a risk.

Drones are one such factor.

While they are clearly essential to the reproduction of the species, drones contribute very little to the actual running of the hive itself. Indeed, when it comes to the consumption of honey they are a negative drain on essential resources. Worker bees see this coming and as the winter approaches, they evict drones from the hive. The idea of carrying "passengers" who simply consume honey through the winter is simply not a viable tradeoff.

So out the drones go. It's a ruthless but essential process, including the physical eviction of drones by worker bees.

Brood Production

Along the same lines, expanding the number of bees in the colony as winter approaches makes little sense. Brood at this time translates into more mouths to feed. This isn't purely a factor of reducing the number of bees consuming the honey reserve, but also reflects the simple truth that in fall there is less nectar and pollen at this time of year anyway.

The net result is that brood rearing is lowered considerably, an intentional act on the part of the colony as it prepares for winter.

Fat Bees

Getting through the winter is a very different challenge than life in the summer. Bees are extremely well adapted to their environment at the best of times and they change their body make up to prepare for the worst of times. Specifically, the approach of winter creates so-called fat bees. Fat bees are winter bees - bees that are much better suited to get through the winter, as follows:

A compound called vitellogenin helps bees store food reserves in their body. This is far less necessary in the summer, when they can freely move to and consume food. But in the winter vitellogenin becomes more important so a fat bee has more.

Lower levels of hormones

Enlarged food glands

Higher level of sugars and fats in their blood

The end result is indeed a fatter bee, but also one that is better able to tolerate and survive the cold weather of winter.

The Winter Cluster

With the preparation done and the cold months arriving, it's time for the colony to "bed in" for the winter. As with most things bee-related, what happens in the apparently still and quiet hive is rather remarkable.

What is the winter cluster?

This is formed when your beehive is surrounded by snow in the winter and your bees are working together to keep a single queen at a comfortable, life-sustaining temperature.

The objective of the winter cluster is simple, namely to reach the spring with a healthy queen and enough workers to restart the foraging and expand the colony all over again. The principle resources they need are warmth and nutrition.

Warmth

Bees are cold-blooded. However, somewhat unusually, they do not simply die off leaving nested eggs to continue the species through the winter. Neither do they hibernate. Instead they remain active all winter, eating and metabolizing honey throughout.

The queen is kept at a steady temperature by essentially being "hugged" by workers throughout the winter. The worker bees will form a cluster - hence the name - around her, enclosing her in a small but warm space. They "shiver" their flight muscles, which creates heat. Across thousands of bees this can create a considerable heat source.

There are some fascinating aspects to the winter cluster.

Bees will be dispersed around the hive while the temperature is around 60 degrees

When the temperature drops below that level, worker bees will start forming a cluster around the queen

The center of the cluster, where the queen resides, will be maintained at a temperature of around 92 F

The "tightness" of the cluster will be adjusted, according to the outside temperature, with a denser cluster being formed as temperatures drop

To ensure that workers on the outside of the cluster don't succumb to the cold, there is a constant movement of workers from the outside to the inside of the cluster, effectively giving all workers a turn in the warmer inner cluster

If the outside temperature passes above 50 F, bees will often take advantage to leave the hive and defecate, thus helping the cleanliness of the hive. These are called cleansing flights.

Exothermic VS. Endothermic...

Each bee is exothermic, since it requires heat from external sources. The colony is endothermic because it heats itself from within.

Nutrition

Staying warm is important but for continued warmth the bees need a source of energy throughout the winter. That is the purpose of the honey reserve they build.

The whole cluster will gradually move around the hive, as one, passing over and consuming honey they have previously stored, fueling their muscle-originated warmth. If temperatures are within certain boundaries, the cluster can move around and "jump" from one part of the honey-laden hive to another.

It is not uncommon, though, for the cluster to be stranded - not able to reach perfectly good honey they have stored because temperatures are too cold, even though they have exhausted resources in the area in which the cluster resides. The loss of a colony due to cold, with a store of honey just out of reach, is a sad demise for the colony.

The winter cluster is a remarkable process though which bees find a way to survive frigid weather, thanks to an extraordinary effort and planning in the warmer months.

15 thoughts on “Fat Bees and the Winter Cluster”

i have just finished the Nov 21 part of the study course. i have found it very interesting and informative. thanks for having me on your study course list. looking forward to more parts, thanks Richard , Davie Florida

Bees are cold-blooded and, as such, absorb – rather than give off – heat. As you say, endothermic means the the absorption of heat, which is what bees do.

Meanwhile, the winter cluster creates (gives off) heat, through the activity of the bees in the cluster, as the bees move their flight muscles. Overall, this means the cluster is endothermic, since it releases heat.

My interpretation of this is that at a certain time in the late fall brood rearing is adjusted by the workers so that the latest and all subsequent eggs are raised to become fat bees. From a certain point onward all emerging pupa are fatties and the bees that were born before that point are destined to die away and not become part of the cluster. So if you see bees doing orientation or foraging in the late fall, those bees won’t make the winter roster. Also means combining a weak hive ( in particular one without a laying queen) with a strong hive late in the fall … is not doing anyone a favor.

Bees are ectotherms (cold blooded) and are thus incapable of maintaining a constant body temperature. They must depend on the temperature of their surroundings to regulate their body temperature. However, they do have the ability to raise their body temperature (but not maintain) by the chemical breakdown of sugars in the honey, releasing the energy stored in the chemical bonds. This energy is used by the bees to vibrate/move wings to warm the colony.

Breaking chemical bonds to release stored energy is an exothermic process…think glove warmers. Endothermic processes take energy from the surroundings and store it in newly formed chemical bonds, which reduces the temperature of the surroundings…think cold pack in a sports trainers med kit.

Endotherms (warm blooded) are capable of maintaining a constant body temperature. They generate heat from within. One method to do so is the chemical breakdown of carbohydrates, like sugars, to release the energy stored in the chemical bonds.

I think there are some terminology issues, but the chemistry doesn’t lie. The enthalpy for the reaction of glucose metabolism (reacting with oxygen) is -2803kj/mol, and that is exothermic.

Jeffery, it all depends on where one lives. I live in Southern British Columbia Canada. Close to the 49th parallel. At this position our winters can be harsh. Winters start in our area about the end of October/November and last until April/May. Mean temperature varies from 10degrees Celsius down to -30C. -30 can last for 3 weeks or there about. You have to consider how feral bees survive in where ever they abide whether it be a hole in a tree or rotten stump or fallen tree on the ground. The comb they build is created in the most efficient pattern based on the surroundings of the hive. We as beekeepers manipulate their home to suit us. It’s my opinion they have a better home with us than they do in the wild. Based on this, as they survive in a tree trunk with no insulation other than what the hive is built in, we can elaborate on this but I doubt we do them any justice. I only insulate the top lid of my hives and wrap them in roofing paper to thwart the wind against the boxes. I also staple a piece of carpet to the underside of the lid that absorbs any moisture created and leave my bottom entrance fully open and the top entrance open for ventilation. I leave about 80 lbs of honey for them in the double brood setup. Have not lost any hives.

Tell Jeffery that 1 inch rigid foam boards work fine. I tie mine on with a couple small 1/4″ nylon ropes, and leave a small gap on each end that I join together with a small bungee cord. This keeps everything tight against the box. I also add another empty box over the inner cover and fill it with fiberglass insulation. A cover without any insulation under it will melt the snow on the lid, but at a cost to the bees. I do have a question about the second picture in this lesson. I’m sure you’ve seen bees drag things out of the hive, dead bees, yellowjackets and reluctant drones. Why put the entrance reducer in upside down so they have to drag it up and over?

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